INVESTIGATION OF STIMULUS-SECRETION COUPLING IN EQUINE SWEAT GLAND EPITHELIA USING CELL-CULTURE TECHNIQUES

When sweat glands isolated from samples of horse skin were explanted a nd cultured under favourable conditions, they could exhibit cellular o utgrowth. This growth could be maintained for 2-4 weeks and these prim ary cultures were then disaggregated and the resultant cell suspension s used to initiate epithelial cell lines. Secretion from intact equine sweat glands is regulated by beta2-adrenoceptors and appears to be me diated by cyclic AMP, but there is evidence that calcium may also play a role. Adrenaline could increase the cyclic AMP content of the cultu red cells and this response was mediated by beta2-adrenoceptors. Adren aline was also able to evoke a small increase in intracellular free ca lcium ([Ca2+]i) but the pharmacology of this response remains obscure. Adrenaline thus activates at least two potentially important second-m essenger signalling pathways which have the capacity to interact, beca use adrenaline-evoked cyclic AMP formation was inhibited if [Ca2+]i wa s raised with ionomycin. The chloride permeability of mammalian epithe lial cells characteristically rises during secretion, and adrenaline c ould increase chloride permeability in the cultured epithelia but the cells did not contain cyclic-AMP-dependent chloride channels and so th is response was mediated by [Ca2+]i.